1. Field of the Invention
The present invention relates to a photoelectrically readable digital micrometer for precisely measuring a micro distance.
2. Description of the Prior Art
One known micrometer uses a method of reading a scale provided in a micrometer drum in case of measurement, so that such micrometer is troublesome for use and has disadvantages such as taking time for measurement and the like. For eliminating this disadvantage, there has been known a digital micrometer, wherein an operation handle, provided for rotating a spindle shaft in case of measurement, is secured to an integrally movable scale plate, and a light source and a light receiving element are arranged by sandwiching the scale plate so as to slide to an outer ring of the micrometer together with the operation handle.
According to this kind of digital micrometer, the value measured is displayed as a digital amount in a counter, and it is very convenient because the value can be immediately read.
In this kind of micrometer, however, if the operation handle and the scale plate are not precisely vertically arranged relative to the spindle shaft, an error is caused in measurement, and particularly, errors between the operation handle and the scale plate accumulate and result in a large error, so that in case of manufacturing such a micrometer, even a small deviation cannot be permitted, and as a result, the manufacture is very troublesome and expensive.